statistics
posted by srinu .
Machines are used to pack sugar into packets supposedly containing 1.20 kg each. On testing a large number of packets over a long period of time, it was found that the mean weight of the packets was 1.24 kg and the standard deviation was 0.04 Kg. A particular machine is selected to check the total weight of each of the 25 packets filled consecutively by the machine. Calculate the limits within which the weight of the packets should lie assuming that the machine is not been classified as faulty.

Assuming that you are using P = .05, you would want 1.96 SEm (standard error of the mean) in either direction.
Mean ± 1.96SEm
SEm = SD/√(n1)